As noted above, the invention particularly is concerned with a novel seal construction and its use in an air purge coupling such as utilized in the "Space Shuttle" vehicle presently being developed for the United States Government. Such air purge couplings provide purged air to various areas of the vehicle prior to launch. Vents in the sides of the vehicle open to let the stale air out as the new or purged air enters the vehicle through the purge couplings.
Once the vehicle is launched, the air purge couplings close, and remain closed and locked throughout the entire vehicle flight. When closed, the purge couplings are required to seal in either direction of air flow. Such area inside the vehicle ultimately is evacuated of air during flight, since as the vehicle ascends, the vents open now and then to equalize the pressure inside to outside the vehicle until finally all the air inside the vehicle is exhausted.